4.2 was only released to kill softmods. You're fine on 4.0 but can go to 4.1 if you want. If you install cios38rev17 and neogamma rev8 you should be pretty up to date. If you get any black screens loading games ensure you have the ios the game needs. You can find out which ios a game needs by searching for tealc's guide on this. Other than that, you're good to go. Ensure you either have bootmii as boot2 or priiloader, though for brick protection.